Author: Kang, H.-S.
Paper Title Page
MOC01
0.1-nm FEL Lasing of PAL-XFEL  
 
  • H.-S. Kang, H. Heo, C. Kim, G. Kim, C.-K. Min, H. Yang
    PAL, Pohang, Kyungbuk, Republic of Korea
 
  The hard X-ray free electron laser at Pohang Accelerator Laboratory (PAL-XFEL) achieved saturation of a 0.144-nm free electron laser (FEL) beam on November 27, 2016, making it the third hard X-ray FEL in the world, following LCLS in 2009 and SACLA in 2011. On February 2, 2017, a saturated 1.52-nm FEL beam was also achieved in the soft X-ray FEL line with an electron beam energy of 3.0 GeV. Finally, saturation of a 0.104-nm FEL beam was achieved on March 16, 2017 using an electron beam energy of 9.47 GeV and K = 1.87. In this paper we present the commissioning result of PAL-XFEL as well as the beamline commissioning results.  
slides icon Slides MOC01 [7.016 MB]  
 
MOP001 Diamond Double-Crystal System for a Forward Bragg Diffraction X-Ray Monochromator of the Self-Seeded PAL XFEL 1
 
  • Yu. Shvyd'ko, J.W.J. Anton, S.P. Kearney, K.-J. Kim, T. Kolodziej, D. Shu
    ANL, Argonne, Illinois, USA
  • V.D. Blank, S. Terentiev
    TISNCM, Troitsk, Russia
  • H.-S. Kang, C.-K. Min, B.G. Oh
    PAL, Pohang, Kyungbuk, Republic of Korea
  • P. Vodnala
    Northern Illinois University, DeKalb, Illinois, USA
 
  An x-ray monochromator for a hard x-ray self-seeding system is planned at PAL XFEL to be used in a 3-keV to 10-keV photon spectral range. The monochromatization in a 5 keV to 7 keV range will be achieved by forward Bragg diffraction (FBD) from a 30-micron-thin diamond crystal in the [110] orientation employing the (220) symmetric Bragg reflection. FBD from the same crystal using the (111) asymmetric Bragg reflection will provide monochromatization in a 3 keV to 5 keV spectral range. In the 7-keV to 10-keV spectral range, a 100-micron crystal in the [100] orientation will be used employing FBD with the (400) symmetric Bragg reflection. Two almost defect-free diamond crystals in the required orientations and thicknesses are mounted in a strain-free mechanically-stable fashion on a common CVD diamond substrate using all-diamond components, ensuring radiation-safe XFEL operations with improved heat transport. We will present results of the optical and engineering designs, manufacturing, and x-ray diffraction topography characterization of the diamond double-crystal system.  
 
MOP015
Demonstration of Harmonic Lasing Self-Seeded Mode for Soft X-Rays Down to 1nm at PAL-XFEL  
 
  • I.H. Nam, H. Heo, H.-S. Kang, C. Kim, G. Kim, C.-K. Min, H. Yang
    PAL, Pohang, Kyungbuk, Republic of Korea
 
  Harmonic lasing is a promising way to provide the beams that can be brilliant, stable and narrow-band. We demonstrate the 3rd harmonic lasing operation in the current configuration with gap-tunable planar hybrid type undulators at soft X-ray beam line at PAL-XFEL. In order to suppress the fundamental resonant radiation, we used a set of phase shifters for optimal condition. This new operation mode can improve the spectral brightness compare to Self-Amplified Spontaneous emission (SASE) mode. In this paper, we report the results of these studies of the harmonic lasing mode for soft X-ray in the wavelength down to 1 nm with the electron beam energy of 3 GeV at PAL-XFEL.  
 
TUP020
Optimization of PAL-XFEL's 3 Bunch Compressor Linac  
 
  • H.-S. Kang, H. Heo, C. Kim, C.-K. Min, H. Yang
    PAL, Pohang, Kyungbuk, Republic of Korea
  • D. Khan, T.O. Raubenheimer, J. Wu
    SLAC, Menlo Park, California, USA
 
  The Pohang Accelerator Laboratory X-Ray Free Electron Laser (PAL-XFEL) consists of a 10 GeV normal-conducting linac delivering an electron bunch to two undulator beamlines and FEL radiation between 0.1 nm (Hard XRay) and 4.5 nm (Soft X-Ray). To provide high quality FEL lasing, it is paramount to optimize the linac settings under the consideration of the collective effects a beam may experience during transport to the undulator. The PAL-XFEL linac consists of four S-band linac sections, an X-band harmonic linearizer proceeding the first linac section, and a three chicane bunch compression system (the very first of its kind in operation). The addition of the third bunch compressor opens the possibility of heightened mitigation of CSR during compression and an increased flexibility of system configuration. In this paper, we outline a procedure to optimize the PAL-XFEL linac under several compression configurations using the particle tracking code Elegant and present its results.  
 
TUP058 Slippage-Enhanced SASE FEL 1
 
  • J. Wu, A. Brachmann, K. Fang, A. Marinelli, C. Pellegrini, T.O. Raubenheimer, C.-Y. Tsai, C. Yang, M. Yoon, G. Zhou
    SLAC, Menlo Park, California, USA
  • H.-S. Kang, G. Kim, I.H. Nam
    PAL, Pohang, Republic of Korea
  • B. Yang
    University of Texas at Arlington, Arlington, USA
 
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
High-brightness XFEL is demanding for many users, in particular for certain types of imaging applications. Seeded FELs including self-seeding XFELs were successfully demonstrated. Alternative approaches by enhancing slippage between the x-ray pulse and the electron bunch were also demonstrated. This class of Slippage-enhanced SASE (SeSASE) schemes can be unique for FEL spectral range between 1.5 keV to 4 keV where neither grating-based soft x-ray self-seeding nor crystal-based hard x-ray self-seeding can easily access. SeSASE can provide high-brightness XFEL for high repetition rate machines not suffering from heat load on the crystal monochromator. We report start-to-end simulation results for LCLS-II project and PAL-XFEL project with study on tolerance. Performance comparison between SaSASE FEL and self-seeding FEL in the overlapping frequency range is also presented.
 
 
WEC04
Progress of PAL-XFEL Undulator Program  
 
  • D.E. Kim, H.-S. Kang, K.-H. Park
    PAL, Pohang, Kyungbuk, Republic of Korea
  • I.S. Ko
    POSTECH, Pohang, Kyungbuk, Republic of Korea
 
  Pohang Accelerator Laboratory (PAL) recently commissioned and started early user service of 0.1 nm SASE-based FEL based on the 10 GeV S-band linear accelerator named PAL-XFEL. One of the key components of the PAL-XFEL is the undulator system which consists of 20 units of Hard X-ray undulators, and 7 units Soft X-ray FELs. The basic design concept is based on the EU-XFEL undulator, but it also requires modification reflecting PAL-XFEL requirements. In this report, PAL efforts to modify, re-design, manufacture, take measurements, tune, install, and commission the undulator system will be summarized.  
 
WEP019
High Stable Pulse Modulator for PAL-XFEL*  
 
  • S.S. Park, H.-S. Kang, S.H. Kim, H.-S. Lee
    PAL, Pohang, Kyungbuk, Republic of Korea
 
  Funding: Work supported by Ministry of Science, ICT(Information/Communication Technology) and Future Planning.
The XFEL of Pohang Accelerator Laboratory (PAL) commissioned the 10 GeV PAL-XFEL project in 2015. The PAL-XFEL needs a highly-stable electron beam. The very stable beam voltage of a klystron-modulator is essential to provide the stable acceleration field for an electron beam. Thus, the modulator system for the XFEL requires less than 50 ppm PFN voltage stability. To get this high stability on the modulator system, the HVPS of inverter type is an important component. The modulator also needs lower noise and more smart. In this paper, we will discuss the design and the test results of the high-stability pulse modulator system.
 
 
WEP041 HLS to Measure Changes in Real Time in the Ground and Building Floor of PAL-XFEL, Large-Scale Scientific Equipment 1
 
  • H. J. Choi, J.H. Han, H.-S. Kang, S.H. Kim, H.-G. Lee, S.B. Lee
    PAL, Pohang, Kyungbuk, Republic of Korea
 
  A variety of parts that comprise large-scale scientific equipment should be installed and operated at accurate three-dimensional location coordinates (X, Y, Z) through survey and alignment in order to ensure optimal performance. However, uplift or subsidence of the ground occurs over time, and consequently causes the deformation of building floors. The deformation of the ground and buildings cause changes in the location of installed parts, eventually leading to alignment errors (ΔX, ΔY, ΔZ) of components. As a result, the parameters of the system change and the performance of large-scale scientific equipment is degraded. Alignment errors that result from changes in building floor height can be predicted by real-time measurement of changes in building floors. This produces the advantage of reducing survey and alignment time by selecting the region where great changes in building floor height are shown and re-aligning components in the region in a short time. To do so, HLS (hydrostatic leveling sensor) with a resolution of 0.2 micrometers and a waterpipe of 1 km are installed at the PAL-XFEL building. This paper introduces the installation and operation status of HLS.  
poster icon Poster WEP041 [0.827 MB]